169. Majority Element

Easy (Dễ) C++ Python 🔗 Xem trên LeetCode

📋 Đề Bài

Given an array nums of size n, return the majority element.

The majority element is the element that appears more than ⌊n / 2⌋ times. You may assume that the majority element always exists in the array.

 

Example 1:

Input: nums = [3,2,3]
Output: 3

Example 2:

Input: nums = [2,2,1,1,1,2,2]
Output: 2

 

Constraints:

  • n == nums.length
  • 1 <= n <= 5 * 104
  • -109 <= nums[i] <= 109

 

Follow-up: Could you solve the problem in linear time and in O(1) space?

🧠 Thuật Toán & Kỹ Thuật

Sorting (Sắp xếp)
⏱️ Thời gian O(n log n)
💾 Không gian O(n)

💻 Lời Giải

C++ 0169-majority-element.cpp 
class Solution {
public:
    int majorityElement(vector<int>& nums) {
        int n = nums.size();
        int vote = 1;
        int candidate = nums[0];
        for (int i = 1; i < n; ++i) {
            if (!vote) {
                vote = 1;
                candidate = nums[i];
            }
            else if (candidate == nums[i]) {
                vote++;
            }
            else {
                vote--;
            }
        }
        return candidate;
    }
};
Python 0169-majority-element.py 
class Solution:
    def majorityElement(self, nums: List[int]) -> int:
        return sorted(nums)[len(nums) // 2]